X3 Helicopter Sets Speed Record At Nearly 300 MPH

When you fly a fast helicopter, you need a fast chase plane. Eurocopter's X3 flies with an L39 Albatross during a test flight. Photo:Alain Ernoult - ERNOULT.COM via Eurocopter

Hervé Jammayrac knows fast.

The Eurocopter test pilot set a new speed record for helicopters last week, achieving 255 knots (293 mph) in the Eurocopter X3 hybrid. That easily eclipsed the benchmark Kevin Bredenbeck set in the experimental (and conincidentally named) Sirkorksy X2 a little more than two years ago.

“It’s no exaggeration to say that the X3 is clearly in its element at high speeds,” he said. “While flying at both 255 knots and 263 knots, the X3 performed exactly as it has throughout its flight envelope, exhibiting outstanding stability and providing a low vibration level without any anti-vibration system.”

The level speed flight of 255 knots was achieved on June 7, but wasn’t announced until today. Before the level flight, which took place at roughly 10,000 feet according to Eurocopter, the team achieved a speed of 263 knots in a descent.

The Eurocopter X2, like the Sikorsky X2, was developed to explore new options for high-speed rotary wing flight. Unlike the X2, which uses a pair of main rotors stacked one atop the other and a pusher propeller at the back, the X3 uses a more traditional main rotor layout and two propellers mounted on small wings on the fuselage. The X3 is based on the Dauphin helicopter used by the United States Coast Guard and others around the world. It first flew in 2010, the same year Sikorsky set the previous record of 250 knots with the X2.

Besides the obvious changes with the tractor propeller setup, the X3 features a drag-reducing rotor head fairing, something Eurocopter and Sikorsky found critical to eking out every last knot. The complex aerodynamics of helicopter flight result in a significant drag where the rotor attaches to the fuselage, and on the rotor head. The fairings reduce drag and allow for extra speed without requiring additional power. The main rotor also presents a major challenge at high speeds because of retreating blade stall, where the blade on the rotor going backward during rotation experiences a drop in airspeed, causing several aerodynamic headaches.

“These flights allow us to further explore the behavior of main rotors at high speeds, and enable us to make effectiveness assessments of the fairing we’ve added to the main rotor hub,” flight test engineer Dominique Fournier said after the flight. “[This] will be beneficial for drag optimization across Eurocopter’s overall product range.”

The X3 toured the United States last year, performing demonstrations for potential civil, military and law enforcement operators. The X3 has flown more than 140 hours in its testing and demonstration programs and will be retired after making a final, static, appearance at the Paris Air Show next week.

With the Sikorsky X2 and Eurocopter X3 retired, the speed race appears over for now. But both companies plan to use the technology in future models. Sikorsky already is working on a design based on the compound rotor and pusher propeller layout of the X2. Eurocopter says the X3 will influence a wide range of models, including helicopters used for long-distance search and rescue, off-shore airlift, border patrol and military missions.